1. Field of the Invention
The present invention relates to an electronic device with a multilayer structure and a method of making the same.
2. Related Background Art
There are conventional thin-film piezoelectric elements being a type of electronic devices in this technical field, for example, as disclosed in Japanese Patent Application Laid-Open No. 2003-229611 and others. For fabricating the thin-film piezoelectric element described in this Application, two silicon substrates are first prepared and a (200) plane preferentially oriented MgO film is deposited on a surface of each substrate. Then a first electrode film, a piezoelectric film, and a second electrode film are successively laid on each substrate with the MgO film thereon, thereby fabricating two multilayer substrates. Then these multilayer substrates are bonded to each other with an adhesive so that their electrode films face each other. Thereafter, only one silicon substrate is removed by etching. Then forming into a predetermined element shape by dry etching or the like and coating with resin, thereafter, the other silicon substrate is removed by etching to complete fabrication of the thin-film piezoelectric element. Related technologies are also disclosed in Japanese Patent Applications Laid-Open No. 2002-164586, Laid-Open No. 2001-313429, and Laid-Open No. 11-312801, and Japanese Patent No. 3310881.
However, the aforementioned conventional electronic device has the following problem. Namely, the step of removing the second substrate by etching sometimes involved permeation of an etching solution through a joint between the coating resin (protecting film) and the laminate comprised of the electrode films and piezoelectric films. If this etching solution permeates up to the piezoelectric film, the piezoelectric film will be dissolved to heavily degrade the characteristics of the piezoelectric element fabricated. It also leads to reduction of yield and reduction of productivity of the electronic device.
The present invention has been accomplished to solve the above problem and an object of the present invention is therefore to provide an electronic device with improved characteristics and a method of making the electronic device.